I need some help in math please.?

Question

A dot on 1 wheel begins it's rotation every 7 mins., and a dot on another begins it's rotation every 5 mins. both wheels begin to rotate at the same time every (?) mins.

a. 1/35

b. 1/7

c. 5/7

d. 1 2/5

e. 35

How do you do it? it took 45mins of y time.

Answer 1

You need to find a common multiple of 5 and 7.

The first wheel will rotate at 7, 14, 21, ...

The second wheel will rotate at 5, 10, 15, ...

In other words, what is the first common number that they will hit?

Answer 2

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